NOVEMBER 2005: Transpacific transport of Asian anthropogenic
aerosols and its impact on surface air quality in the United States
We use satellite (MODIS) observations of aerosol optical depths (AODs) over
the North Pacific, together with surface aerosol measurements at a network
of remote U.S. sites (IMPROVE), to improve understanding of the transpacific
transport of Asian aerosol pollution and assess the ability of a global 3-D
chemical transport model (GEOS-Chem CTM) to quantify Asian aerosol
enhancements in U.S. surface air.
We find that Asian pollution preferentially impacts the northwestern United
States and that mean Asian pollution enhancement in that region in spring is 0.16 µg
m-3 with a ±50% unccrtainty suggested by the correlation of model results with
observations. This is higher than the estimated natural concentration of
0.09 µg
m-3 presently used as objective for regulation of visibility in U.S.
wilderness areas.
A full description is given in Heald et al., 2005b.
Figure: Transpacific sulfate event of April 2001, where the patterns and timing of
sulfate transport agree with enhancements in total AOD as observed by MODIS.
MODIS AODs (550 nm) are compared to the GEOS-Chem dust and sulfate AODs, and
to the CO columns observed by MOPITT (x1018 moleculescm-2).
|